C++/Function/Function Arguments

A example of default arguments.

<source lang="cpp">

1. include <iostream>

using namespace std; void f(int a=0, int b=0) {

 cout << "a: " << a << ", b: " << b;
 cout << "\n";

} int main() {

 f();
 f(10);
 f(10, 99);
 return 0;

}

 </source>

Compute area of a rectangle using default arguments.

<source lang="cpp">

1. include <iostream>

using namespace std;

double rect_area(double length, double width = 0) {

 if(!width) 
    width = length;
 return length * width;

} int main() {

 cout  << "10 x 5.8 rectangle has area: ";
 cout << rect_area(10.0, 5.8) << "\n";
 cout  << "10 x 10 square has area: ";
 cout << rect_area(10.0) << "\n";
 return 0;

}

 </source>

Default function arguments

<source lang="cpp">

1. include <iostream>
2. include <string>

using namespace std; int askNumber(int high, int low = 1); int main() {

   int number = askNumber(5);
   cout << "Thanks for entering: " << number << "\n\n";
   
   number = askNumber(10, 5);
   cout << "Thanks for entering: " << number << "\n\n";
   return 0;

} int askNumber(int high, int low) {

   int num;
   do
   {
       cout << "Please enter a number" << " (" << low << " - " << high << "): ";
       cin >> num;
   } while (num > high || num < low);
   return num;

}

 </source>

Use default argument

<source lang="cpp">

1. include <iostream>

using namespace std; class myclass {

 int x;

public:

 myclass(int n = 0) { 
    x = n; 
 }
 int getx() { 
    return x; 
 }

}; int main() {

 myclass o1(10);          // declare with initial value
 myclass o2;              // declare without initializer
 cout << "o1: " << o1.getx() << "\n";
 cout << "o2: " << o2.getx() << "\n";
 return 0;

}

 </source>